Lift installation



July 5, 1955 1. v. K. HOTT r-:TAL 3,258,920

LIFT INSTALLATION Filed May lO, 1963 3 Sheets-Sheet 1 INVENTORS /oN In K. HOTT DAV/0 M. GOLDzw/G WHERE/V E. wies T521 205527 J. Hmm/X 3 Sheets-Sheet 2 LIFT INSTALLATION l. V. K. HOTT ETAL Filed May lO, 1963 July 5, 1966 MEM 6 ogn@ m wauw m WHJ wv T Nxnmw 4 IVMEE vee 0440 fc /DWK July 5, 1966 l. v. K. HOTT ETAL 3,258,920

LIFT INSTALLATION Filed May lO, 1963 3 Sheecs-Sheerl 3 United States Patent O 3,258,920 LIF'I` INSTALLATION Ion V. K. Hott, David M. Goldzwig, Warren E. Webster II, and Robert J. Haddix, Dayton, Ohio, assignors to The Joyce-Cridland Company, Dayton, Ohio, a corporation of Ohio Filed May 10, 1963, Ser. No. 279,568 6 Claims. (Cl. 60-52) This invention relates to a lift installation and more particularly to means for controlling the operation of the vlift jacking units of a two post hydraulic vehicle lift. However, as will appear below, the invention is not necessarily so limited.

An object of this invention is to provide an improved control structure for a two post vehicle lift installation.

Another object of this invention is to provide an improved control structure for a two post vehicle lift in which a single operating lever can be used -to meter the supply of fluid to the two jacking units utilizing only a single control valve.

Still another object of this invention is to provide a control structure for a two post vehicle lift installation utilizing a pair of manually operable control members, one of which controls the elevation of the two lift posts simultaneously and the other of which controls lthe relative positions of the two posts.

A further object of this invention is to provide an improved control `structure for a vehicle lift which utilizes a magnetic proximity switch to automatically control an electric pump. The operating parts of the proximity switch are all enclosed within a sealed housing. Accordingly, much longer life of the switch can be expected than with ordinary switches in the environment of a vehicle lift.

Other objects and advantages reside in the construction of parts, the combination thereof, the method of manufacture and the mode of operation, as will become more apparent from the following description.

Referring to the drawings:

FIGURE 1 is a plan view, with parts broken away, of a two post vehicle lift control structure made in accordance with this invention.

FIGURE 2 is a transverse cross-sectional view, with parts broken away, of the control structure shown in FIGURE 1 taken along line 2-2 thereof.

FIGURE 3 is a longitudinal sectional view of the control structure of FIGURE 1 taken -along line 3--3 thereof.

FIGURE 4 is an exploded perspective view of a metering valve used in the control structure of FIGURE 1.

FIGURE 5 is a cross-sectional view of the metering Valve of FIGURE 4 as viewed in the direction of arrows 5-5 of FIGURE 1.

FIGURE 6 is a cross-sectional view of a portion of the metering valve of FIGURE 4, as viewed in the direction of arrows 6-6 of FIGURE 3.

FIGURE 7 is a plan view, with parts broken away, of a modied control structure made in accordance with this invention. FIGURE 7 also shows an oil reservoir for use with the lift installation.

FIGURE 8 is a side elevational view of the structure of FIGURE 7, with parts broken away and in cross-section.

FIGURE 9 is a transverse cross-sectional view of the embodiment of FIGURE 7, taken along the line 9 9 thereof.

FIGURE 10 is a schematic representation of a complete two post vehicle lift installation using the control structure shown in FIGURE 1.

FIGURE 11 is a simplified schematic representation of 3,258,920 Patented July 5, 1966 an electric circuit for energizing an oil supply pump used in connection with the control structure of FIGURE 1.

A control structure, generally designated 10, is illustrated in FIGURES l1 through 3, which control structure is to be used in association with a two post vehicle lift installation. As well known, a two post vehicle lift installation includes a pair of jacking units, each comprising a cylinder which receives a piston or ram. The control structure shown in FIGURES 1 through 3 is designed for use with jacking units known as full hydraulic. A full hydraulic lift or jacking unit relies upon the introduction ofl oil or other hydraulic media into the lift cylinder to force the piston or ram upwardly. In this case, the oil is forced into the lift cylinders Iby an electric pump.

Referring 4to FIGURE 10, which illustrates a lift installation employing the control structure 10 made in accordance with this invention, oil is pumped by an oil supply pump P from a reservoir R through 4a liuid inlet conduit 12, an inlet valve 14, and a fluid conduit 16 leading from the inlet valve 14 to a metering valve 18. Two conduits 20 direct fluid from the metering valve 1S to the two diiferent jacking units J1 and J2. As apparent, if the pump l is operating to direct oil through the conduit 12 while the inlet valve 14 is open, oil will pass through the metering valve 18 lto the cylinders of the jacking units I1 and I2 in order to raise the lift pistons or rams. The oil is dumped back into the reservoir R through an outlet conduit 22, which is connected between the metering valve 18 and an outlet or discharge valve 24 to a discharge conduit 26. Assuming the inlet valve 14 to be closed and the discharge valve 24 to be open, oil will pass from the jacking units Il and J2 through conduits 20, the metering valve 18, the conduit 22, the discharge valve 24 and the discharge conduit 26 to the reservoir R.

Referring to FIGURES l, 2 and 3, the control structure, including the valves 14, 18 and 24, may be mounted in a housing, generally designated 30, having opposed rearward and forward end walls 32, 34, respectively, side walls 36, 38 connected therebetween, and a cover member 40. The entire housing 30 may be located within a pit in the earth or oor with the cover member 40 ush with the top thereof. As apparent from an inspection of FIGURES 1 through 3, the conduits 12 and 26 are supported by the rearward end wall 32 while the metering valve 18 and its associated conduits 20 are supported by the forward end wa'll 34.

The inlet and discharge valves 14 and 24 may be conventional and include valve plates (not shown) spring biased by means of springs located in spring housings 42 and 44, respectively, which `bias the valve plates to a valve closing position. As shown in FIGURES 2 and 3, the operating mechanism for the discharge valve 24, which serves to overcome the bias provided by the spring within the housing 44, comprises a generally horizontally disposed 4arrn 50 having a downwardly extending sleeve portion 52 which encircles a valve operating rod 53. The arm 50 is further provided with a pair of upwardly extending flanges on the forward portion thereof forming a yoke 54 which supports an axle 56 upon which \a roller element 58 is mounted. The sleeve portion 52 is rigidly affixed to the rod 53 so that the spring located within the housing 44 positions the arm 50 such that the yoke portion 54 thereof extends generally vertically, -as shown in FIGURE 2. The valve control member for the valve 14 comprises a similar structure including an arm 60 having an upwardly extending yoke portion 64 supporting a roller element 68 on an axle 66 and a downwardly extending portion 62 connected to a valve operating rod 63. The v-alve members 14 and 24 may be identical, but are mounted on the conduits 12 and 26, respectively, in

opposite directions so that pivotal movement of either of the arms 50 or 60 toward the center of the housing 30 will in each case serve to open its associated valve.

Referring to FIGURE 2, the roller elements SS and 68 are engaged and actuated by a pair of treadle arms 70 and 72, each of which is mounted for rotation about a pivot pin 74, which in turn is mounted upon a U-shaped bracket 76 (FIGURE 3) welded to a generally horizontal support piece 78. The treadle arms 70 and 72 are each provided with adjusting screw and nut assemblies 80 'and 82, respectively, which are engaged by ears 34 and 86, respectively, mounted on opposed sides of a treadle 88, which also is mounted for pivotal movement about the pivot pin 74. An elongate manual val've actuating lever 90 is mounted for sliding movement within -an aperture in the treadle 88 in a fashion similar to that described in a copending application for United States Letters Patent, Serial No. 201,151, led on June 8, 1962 by Ion V. K. Hott. As apparent from an inspection of FIG- URES l and 2, if the actuating lever 90 is extended upwardly of the housing 30, it can conveniently be used to pivot the treadle 88 about the pivot pin 74. Such pivotal movement will result in selective opening of the valve 14 or the valve 24. For example, if the treadle 88 is pivoted downwardly, as viewed in FIGURE 1, in the direction of the UP arrow, the oil inlet valve 14 will be opened. Similarly, the discharge valve 24 is opened if the treadle 88 is pivoted upwardly as viewed in FIGURE 1.

It is necessary to actuate the oil supply pump P at approximately the same time las the Valve 14 is opened in order to pump Oil to the metering valve 18. In accordance with this invention, downward pivotal movement of the treadle 88, as viewed in FIGURE l, serves to open a switch which controls the oil supply pump. As shown best in FIGURES l and 2, a magnetic proximity switch 100 is aixed as by a clamp 102 to a bracket 104, which in turn is mounted upon the support piece 78. The proximity switch 100 is connected by a conduit enclosed within piping 101 in an electric pump control circuit, shown schematically in FIGURE 11 as including a source of electrical energy, the proximity switch contacts 10011 and the pump P. The details of construction of the proximity switch 100 are not disclosed herein, since a variety of conventional proximity switches could be used.

Importantly, the proximity switch contacts 100a are` enclosed within a sealed housing. Since the operating parts of the switch |are so enclosed and thus protected from damage, the switch can be relied upon for a longer useful life. The electric circuit for energization of the pump P could be designed to use a switch 100 having normally closed contacts. For simplicity, the proximity switch 100 illustrated is the type in which switch contacts 100a (FIGURE 11) are normally open when a ferromagnetic plate is closely adjacent to or contacting the forward face, designated 106, thereof. Should the ferromagnetic plate be removed from the area of the front face 106 of the proximity switch 100, the switch contacts 10061 therein will close. In accordance with this invention, a ferromagnetic switch operating plate 108 is suspended from a sleeve 110 mounted for pivotal movement on the pivot pin 74 forwardly of the treadle 88. The lower end of the plate 108 is biased by a spring 112 axed at one end thereto and at its other end to the bracket 104. Consequently, the plate 108 is normally held in engagement with the forward face 106 of the proximity switch 100, whereby the switch contacts 100:1 are open.

The treadle 88 includes a pair of depending side plates 88a and 88b straddling the U-shaped bracket 76. A switch actuating lug 114 is yaffix-ed to the exposed face of the side plate 88a so that when the treadle 88 is in its neutral position, as illustrated in the drawing, the lug 114 is to the left (as viewed in FIGURE 2) of the plate 108. Depending from the sleeve is a cooperating lug 116 which is substantially coplanar with the plate 108. As apparent, counterclockwise pivotal movement of the treadle 8S, as viewed in FIGURE 2, causes the lug 114 to engage the lug 116 to pivot the plate 108 about the pivot pin 74 in a counterclockwise direction, thus removing it from the area of the forward face 106 of the proximity switch 100. Accordingly, when the valve 14 is open, the oil supply pump is energized. When the treadle 88 is returned to its neutral position, the spring 112 returns the plate 108 t/o its position in contact with the switch 100. Note that clockwise pivotal movement of the treadle 88, as viewed in FIGURE 2, does not affect the position of the plate 108. Of course, it is unnecessary for the pump to be operating when the discharge or outlet valve 24 is opened.

Referring to FIGURES 4, 5 and 6, the metering valve 18 includes a base xture 120, having a threaded inlet port 122 and a pair of threaded outlet ports 124. As shown in FIGURE 3, a vertical fluid conduit 126 is connected to a union 128 to which the uid conduits 16 and 22 are connected. The member 126 in turn is in threaded connection with the inlet port 122. The previously described conduits 20 connect the two outlet ports 124 to the two jacking .units J1 and J2.

The upper surface of the base fixture forms a stationary valve plate, designated 130, and is provided with three apertures therein, one aperture, designated 132, being in direct communication with the inlet port 122. The other two apertures, designated 134, are connected separately to the outlet ports 124 (see FIGURE 6). The centers of the apertures 132 and 134 are separated by substantially 120 each from the others and are substantially equally spaced about a vertical axis passing generally centrally through the plate 130. The ow of fluid through the apertures 134 is controlled by a rotatable valve plate 136 having an inlet aperture 138 and two outlet apertures 140. The bottom surface of the plate 136 abuts the valve plate 130. The top surface of the valve plate 136 is provided with an arcuate recess 145 communicating between the three .apertures 138 and therein. A valve cap 142, which is connected to the base fixture 120 as by a plurality of bolts 144, is provided with a recess receiving the rotatable valve plate 136 and holds it in engagement with the valve plate 130. To prevent leakage of oil, a sealing ring 146 is located within a recess 148 within the top surface of the base fixture 120. The cap 142 is provided with an arcuate recess 150 cooperating with the recess in the top surface of the plate 136 to form a cavity enabling the free flow of oil from the aperture 138 equally to both apertures 140.

As diagrammatieally illustrated in FIGURE 6, the apertures 134 are located on centers which are more widely spaced than are the centers of the apertures 140. The apertures 138, on the other hand, is located on the same center as the aperture 132. As apparent, rotation of the valve plate 136 about its center in either direction would creats an area of greater overlap, and hence, greater fluid ilow, through one aperture 140 and its associated aperture 134 then the other pair of apertures 140 and 134. Further rotation of the valve plate 136 would block the flow of fluid between one of the apertures 140 and its associated aperture 134. Thus, the rate of fluid ow through the two outlet ports 124 may be varied by rotation of the valve plate 136.

Rotation of the valve plate 136 is accomplished by means of a valve control rod 160, having its lower end tixedly connected to the center of the valve plate 136 as 'by a set screw 162. The control rod 160 extends vertically upwardly through an .aperture 164 in the valve cap 142 and through an aperture 166 in the cover member 40 (see FIGURE 3). The top of the control rod is connected to a metering valve control handle 168 by means of a pin and slot connection, `generally designated 170. The extent of rotatable movement of the valve plate 136 is limited by a stop pin 172, which is adapted to -strike a stop lug 174 extendingupwardly from the housing cap 142. As apparent, the control handle 168 can be rotated in either direction from the neutral position, which is diagrammatically illustrated in FIG- URE 6, to either of two extreme positions to cut oif the ow -of fluid to either of the ports 124. If desired, a coil spring 184 may be aiiixed to the cap 142 and one of the pins 172 to bias the valve control rod 160 to its neutral position. The spring 184 is designed to be relaxed in the neutral position and is placed under either tension or compression when the control rod 160 is rotated. The control handle 168 is normally locked in a neutral position by means of a latch pin 176 welded to a pivot pin 178 (FIGURE 7) on the outer end thereof, the latch pin 17 6 having a downwardly extending rearward portion 180 which passes into an aperture 182 in the cover member 40. Briefly, the operation of the structure described above is as follows. Assuming the parts are positioned as shown in FIGURE 2, the lever 90 is extended upwardly of the housing 30 and moved in a counterclockwise direction to pivot the treadle 88 in the direction of the UP arrow shown in FIGURE 1. The lug 114 thereupon engages the cooperating lug 116 on the sleeve 110, whereby the plate 108 is withdrawn from the area of the front face of the proximity switch 100. Consequently, switch contacts 100a are closed whereupon oil is pumped by the oil supply pump P into the fluid inlet conduit 12. At the same time, the inlet valve 14 is opened, whereupon oil from the reservoir R passes through the metering valve 18 into the two jacking units Il and I2. Since the valve control handle 168 is locked in its neutral position, due to the engagement of the pin portion 180 within the cover me-mber aperture 182, the oil flow to the two jacking units will be substantially equal.

If it is desired for one reason or another to elevate one yof the jacking units at a faster rate than the other, the valve control handle 168 may be removed from its neutral position by pivotal movement of the latch pin 176 and rotation of the control handle 16S in the desired direction. As soon .as the jacking units reach `the desired height, the lever 90 is returned to its central position whereupon both valves 14 and 24 are closed and the jacking units held in their raised position. As the treadle 88 is returned to its neutral position, the switch operating plate 108 is returned into engage-ment with the front face of the proximity switch 100, thereby deenergizing the oil supply pump P. The jacking units can then be lowered by pivoting the treadle 88 in a clockwise direction, as Viewed in FIGURE 2, thereby opening the valve 24, whereupon the weight of the pistons and the vehicle carried thereby force the oil back through the conduits 20, the metering valve 18, the outlet conduit 22 the valve 24 and the discharge conduit 26, The relative rate of descent of the two pistons or rams can be controlled by movement of the handle 168 as described above. If desired, suitable notations can be marked on the cover member 40 to indicate the direction in which the valve control handle 168 should be rotated to selectively control the two jacking units.

Referring to FIGURES 7, 8 :and 9, .a control structure 200 is shown therein for use with the type of hydraulic lift in which oil is forced into the lift cylinders by compressed air. Air under pressure is supplied to the top of an oil reservoir 202 through an air inlet port 204 forcing oil through an outlet port 206 and a uid conduit 208 to the base of a metering valve 210, which may be identical to the valve 18 previously described, `and finally through a pair of outlet ports 212 into uid conduits 214 leading to the jacking units (not shown). To raise the pistons associated with the jacking units, air under pressure is supplied by .a compressor (not shown) through an air inlet conduit 216, an air inlet valve 218 and an air conduit 220 to the port 204. The pistons may be subsequently lowered by dumping the air to atmosphere on opening of an air outlet valve 222, which directs air through a muffler 224 to atmosphere. The air inlet valve 218 and the 4air outlet valve 222 may be mounted in a common housing 228 and are controlled by a pair of spring biased valve stems or plungers, namely an air inlet plunger 230 and an air exhaust plunger 232. Both plungers 230 and 232 are spring biased upwardly. Should the inlet plunger 230 be depressed, air under pressure will be forced through the air conduit 220 into the uid reservoir 202. Similarly, should the exhaust plunger 232 be depressed, air will be exhausted from the reservoir 202 through the air conduit 220 and the muer 224 to atmosphere. This type of valve structure is the com-mon poppetV valve structure which may be controlled by means of a treadle mechanism, generally designated 240, which employs a valve stem rocker arm 242 mounted for pivotal movement about a horizontal axis upon a pivot pin 244 passing through 1a generally vertical support rod 246 which is integral with the valve housing 228. The valve stem rocker arm 242 is of -a conventional type having opposed lower surfaces adapted to engage the valve stems or plungers 230 and 232. The upper .arcuate surface of the rocker arm 242 is generally concave and is adapted to be engaged by opposed depending arms 248 forming a part of a treadle 250 mounted for rotation about a horizontal axis upon vertically upwardly extending arm p0rtions 252 of the rod 246 by means of a treadle pivot pin 254. It will be noted in FIGURE 8 that the axes of rotation of the rocker :arm 242 .and the treadle 250 are parallel. Accordingly, counterclockwise pivotal movement of the treadle 250, as viewed in FIGURE 9, causes counterclockwise pivotal movement of the rocker arm 242, forcing the inlet valve stem or plunger 230 downwardly. Clockwise rotation of the treadle 250, as viewed in FIG- URE 9, similarly forces the discharge valve stern or plunger 232 downwardly.

As in the embodiment described in relation to FIG- URES 1 through 7, movement of the treadle 250 is controlled by a treadle control lever having an elongate rod portion and a hollow cylindrical knob portion connected thereto. The rod portion is again received for vertical sliding movement within :a rectangular bore formed at an inclined angle in the body of the treadle 250.

The operation of the mechanism described in relation to FIGURES 7 through 9 is believed obvious. Again, the metering valve control handle, designated 260, can be used selectively to control the movement of the two jacking units. In this embodiment, the air compressor would have to -be separately energized. However, it is apparent that a suitable switch could be associated with the treadle 250, as in the embodiment of FIGURES 1 through 7, to energize the air compressor.

The handle members 168 and 260 can be operated by a conventional elongate hooked actuating rod (not shown) by insertion of the hooked portion thereon within a pocket or recess portion, designated 168g in FIGURE 1 and 260a in FIGURE 7, of the respective larms 168 and 260. The pins 176, which have rearwardly extending portions 17611, will thereupon automatically pivot about the pins 176 whereupon the latches provided by the pins 176a can be released. The aforementioned actuating rod may also be used to actuate the valve actuating levers 90, which are provided with hollow knob portions, `as described in said application for United States Letters Patent Serial No. 201,151. The conventional actuating rod is of the type shown in FIGURE 5 of my copending application for United States Letters Patent, Serial No. 227,415, tiled on October 1, 1962.

Although the presently preferred embodiment of the device has been described, it will be understood that within the purview of this invention various changes may be made in the form, details, proportion and arrange-ment of parts, the combination thereof 4and mode of operation, which generally stated consist in a device capable of carrying out the objects set forth, as disclosed and dened in the appended claims.

Having thus described our invention, we claim:

1. In `a vehicle lift installation, the combination corn prising: a fluid operated jacking unit; a fluid reservoir; an electrically driven pump for pumping uid to said jacking unit; a normally closed inlet valve located between said jump and said jacking unit; manually operable means including a treadle movable for opening said inlet valve to permit fluid to ow to said jacking unit; a proximity switch ladapted to energize said pump, said proximity switch including .a pair of switch contacts which open and Close upon movement of a ferromagnetic element adjacent a surface portion thereof; a ferromagnetic plate pivotally mounted adjacent said surface portion; means biasing said plate into a predetermined position relative to said surface portion; and means connecting said treadle and said plate causing said plate to pivot away from said predetermined position upon movement of said treadle, whereby the opened or closed condition of said switch contacts is changed.

2. The combination of claim 1 wherein an elongate Valve actuating lever is slidably mounted for generally vertical movement within an aperture in said treadle, said lever having a hollow knob portion adapted to be engaged and actuated by an actuating rod.

3. In a vehicle lift installation, the combination cornprising: `a pair of fluid operated jacking units; a fluid supply pump; fluid conduit means connecting said supply pump to said jacking units; a normally closed control valve connected by said conduit means between said pump and said jacking units; a uid metering valve connected by said conduit means between said control valve and said jacking units, said metering valve having a single inlet port and two outlet ports, said conduit means including a single conduit member between said control valve and said inlet port and a pair of conduit members, one of said pair extending from one of said outlet ports to one of said jacking units and the other of said pair extending between the other of said outlet ports and the other of said jacking units, and control means connected to said metering valve selectively to control and apportion the iluid flow from said single conduit member to said pair of conduit members simultaneously to control the operation of said jacking units.

4. The combination of claim 3 wherein said metering valve includes a fixed valve plate having three spaced apertures therein on centers substantially equally spaced about an axis normal to the upper surface thereof, one of said apertures being in direct communication with said inlet port and the others of said apertures being in direct communication with separate ones of said outlet ports, and a rotatable valve plate having three apertures therein generally aligned with the apertures in said xed valve pla-te; and wherein said control meansk include a control element connected to said rotatable valve plate adapted .to rotate the same about said axis, the separation between the centers of said others of said apertures in said xed valve plate being different from the separation of the centers of the apertures in said rotatable valve plate which are in general alignment therewith whereby rotation of said valve plate causes a greater area of overlap between one pair of generally aligned apertures than the other pair of generally aligned apertures.

5. The combination of claim 4 wherein said control element comprises a rod connected to said rotatable valve plate and a handle connected to said rod for manual actuation thereof, and wherein latch means are provided to retain said handle in a predetermined position.

6. The combination of claim 5 wherein Said handle is provided with a recess to receive an actuating rod to enable remote operation thereof, and wherein said latch means includes a pivoted pin portion projecting into said recess which is pivoted to release said latch means upon entry of an actuating rod portion into said recess.

References Cited by the Examiner UNITED STATES PATENTS 669,475 3/1901 Bullard 74-539 1,136,589 4/1915 Davis 137-62546 1,484,266 2/1924 Holzbauer 74-539 1,491,077 4/1924 Beerworth 251-293 X 1,836,740 12/1931 Albers IS7-636.1 X 1,907,208 5/1933 Lebel 60-52 1,975,278 10/1934 Lebel 60-52 2,311,864 2/1943 Parsons. 2,582,565 1/1952 Schnippel et al 60-52 2,681,077 6/1954 Hott et al 137-636 2,847,181 8/1958 Muller 251-101 X 2,964,060 12/1960 Sargent 137-634 2,988,108 6/1961 Malmquist et al. 137-625.46 3,022,398 2/1962 Abel 200-87 3,053,050 9/1962 Sommerer 60-51 JULIUS E. WEST, Primary Examiner. 

1. IN A VEHICLE LIFT INSTALLATION, THE COMBINATON COMPRISING: A FLUID OPERATED JACKING UNIT; A FLUID RESERVOIR; AN ELECTRICALLY DRIVEN PUMP FOR PUMPING FLUID TO SAID JACKING UNIT; A NORMALLY CLOSED INLET VALVE LOCATED BETWEEN SAID JUMP AND SAID JACKING UNIT; MANUALLY OPERABLE MEANS INCLUDING A THREADLE MOVABLE FOR OPENING SAID INLET VALVE TO PERMIT FLUID TO FLOW TO SAID JACKING UNIT; A PROXIMITY SWITCH ADAPTED TO ENERGIZE SAID PUMP, SAID PROXIMITY SWITCH INCLUDING PAIR OF SWITCH CONTACTS WHICH OPEN AND CLOSE UPON MOVEMENT OF A FERROMAGNETIC ELEMENT ADJACENT A SURFACE PORTION THEREOF; A FERROMAGNETIC PLATE PIVOTALLY MOUNTED ADJACENT SAID SURFACE PORTION; MEANS BIASING SAID PLATE INTO A PREDETERMINED POSITION RELATIVE TO SAID SURFACE PORTION; AND MEANS CONNECTING SAID TREADLE AND SAID PLATE CAUSING SAID PLATE TO PIVOT AWAY FROM SAID PREDETERMINED POSITION UPON MOVEMENT OF SAID TREADLE, WHEREBY THE OPENED OR CLOSED CONDITION OF SAID SWITCH CONTACTS IS CHANGED. 